Ruby on Rails

We can do class_eval & instance_eval using following syntax, In this example, class_eval? method can be accessed my any objects of the String class. Where as instance_eval? method can be accessed by only String class.  More clearly, class_eval creates instance methods, but instance_eval creates class methods or it can be applied to only one object at a time. [3] pry(main)> String.class_eval? NoMethodError: undefined method `class_eval?' for String:Class Did you mean?  class_eval from (pry):3:in `<main>' [4] pry(main)> String.instance_eval? => true [5] pry(main)> String.new.class_eval? => true my_string = "This is a string" For example you can simply do like below as any string is an object of String Class [5] pry(main)>  my_string .class_eval? => true But you can not do  [7] pry(main)> my_string.instance_eval? NoMethodError: undefined method `instance_eval?' for "This is a string":String